Hydrolysis of organic esters



Patented Oct. 27, 1936 UNITED STATES PATENT OFFICE -No Drawing.

Application April 26, 1933, Serial No. 668,068. In Great Britain May 6, 1932 8 Claims.

This invention'relates to improvements in the hydrolysis of organic esters, and is more particularly concerned with processes for the saponification of cellulose acetate'or other esters of cellulose.

The saponification of cellulose acetate filaments, threads, yarns, ribbons, fabrics or other materials, particularly when aqueous sa'ponifying agents are employed, frequently results in a substantial loss in the tenacity of the yarn, and the principal object of the present invention is to modify the saponifying medium in such a way that loss-in tenacity is decreased or eliminated.'

By applying the processes of the invention the tenacity of the yarns may even increase.

According to the present invention saponification is effected in the presence of an oil which is preferably contained in the saponifying medium itself. The oil may be of mineral, vegetable or animal character, and may be soluble or insoluble in the bath. Thus, for instance, soluble oils include sulphonated castor oil and other vegetable oils suiliciently sulphonated to be soluble in an aqueous bath.

The insoluble oils, for example hydrocarbon oils, such as paraflin or other fractions of petroleum or the aromatic or cyclo-aliphatic hydrocarbons and also vegetable oils, and particularly the non-drying oils, for example castor oil, olive oil, cocoanut oil, arachis oil, and semi-drying oils, for instance cotton seed oil and rape oil, and animal oils, e. g. whale oil, may be emulsified in an aqueous saponifying medium. Thus, for in-.

stance, they may be emulsified with the aid of soaps, sulphonated fats or oils or salts thereof, such as sulphonated castor oil, true sulphonic acids of aliphatic hydrocarbons or alcohols or of fatty acids or salts thereof, the salts and condensation products of amines, particularly amines containing hydroxy, carboxy or other hydrophile groups, with resin and naphthenic acids and higher fatty acids e. g. ethanolamine and other alkylolamine soaps and amino-alkylamides of higher fatty acids and in the aromatic series naphthalene sulphonic acid compounds and particularly alkylated naphthalene sulphonic acids, such as propyl and isobutyl naphthalene sulphonic acids and the sulphonated condensation products of formaldehyde and naphthalene. The use of soaps whether of' inorganic bases or of organic bases is particularly advantageous, since these exert a buffer action on the saponifying treatment in addition to being useful for emulsifying the insoluble oils.

The invention is not confined to the use of aqueous saponifying media, since alcoholic or aqueous alcoholic media may also be employed. When alcoholic media are employed the saponifying agent may be present in a quantity less than that theoretically necessary to effect the v5, desired degree of saponiflcation, as is described in British Patent No. 125,153 and U. S. appliestion S. Nos. 283,999 and 284,000 filed 8th June, 1928. The invention is however of the greatest advantage in relation to aqueous saponifying 10 media, since these media are most potent in bringing about decrease in the tenacity cf the threads.

The saponifying agent may be caustic soda, caustic potash or an alkali salt or other inorganic 15 reagent, for example sodium silicate or tri-' sodium phosphate. Such agents may be used in a proportion appropriate to bring about the desired degree of saponification.

The concentrations of saponifying agent em- 20 ployed may vary widely, depending upon the degree of saponification it is required to efiect, the nature of the saponifying agent employed, the temperature of saponiflcation and other fac- ,tors. Thus relatively low concentrations of 25 caustic soda or caustic potash, for example concentrations of 25% or .5% may be employed at normal or slightly elevated temperatures when materials are treated for comparatively long periods in hank or other package form or as 30 fabrics, particularly when only a small degree of saponification is required, while when it is desired to treat filaments, yarns or similar materials during the course of their travel from one' point to another, for example continuously with 35 their production and/or with a stretching oper-- ation, higher concentrations and/or higher temperatures may be employed, for example concentrations-of 3 to 5% or even up to 10-16% or more of caustic alkali at temperatures of 50 44) to or C. when such temperatures and concentrations are employed in connection with bath treatments, the time of contact of the materials with the bath will in general be relatively short, for example of the order of 10 or 30 seconds 45 or a minute or thereabouts. The exact period will of course depend upon the degree of saponification desired. Saponification processes of this nature are very suitably carried out in a bath having a length of, for example, to 50 feet, so that a rate of travel of the materials of 30 to 50 or even 100 metres per minute may be obtained. In the case of using high concentrations of caustic alkali it is desirable that bufier agents, as for example sodium acetate, sodium 55 chloride or soaps, should be present in order to minimize any deleterious action of the alkali upon the" materials. The bufier agent employed should not be of such a nature or used in such quantities as to throw soluble oils out of solution or break down the emulsion, when an insoluble oil is employed. The use, in addition to the main saponifying agent, of another agent of less alkalinity e. g. lime in the form of a milk or fine suspension or other agent, such as cal cium carbonate, baryta, barium carbonate or the like enables considerably-improved results to be obtained and also enables the concentration and total quantity of caustic soda or other sponifying agent to be reduced. This novel process is described in my U. S. application S. No. 655,778 filed 8th February, 1933. When such substances are used, the considerations mentioned above in connection with buffer agents also arise. Thus the substances employed should be chosen so that insoluble compounds are not formed, and for this reason the sulphonated and preferably highly sulphonated oils are of great value, either to act themselves as oils or as emulsifying agents when insoluble oils are employed.

The concentrations of saponifying agents are referred to above particularly in relation to bath treatments. Where 2. padding treatment or other means of mechanical impregnation is employed high concentrations of saponifying agents for example 15 to 20% or even more may in general be employed, since according to such methods of treatment the yarn is not in contact with large quantities of saponifying medium for any length of time, and the method of application enables uniform distribution of the saponifying' agent in the desired quantities to take place. The saponification may be conducted at about normal atmospheric temperature, or at somewhat elevated temperatures, for example up to 60 C.

or even more.

The saponifying medium employed may, if desired, contain a solvent or swelling agent for the materials under treatment, as for example any of the substances mentioned below in connection with stretching. Alternatively the materials may be treated with solvents or swelling agents prior to saponification, or when saponification is carried out continuously with stretching or other treatment in which the materials are obtained in a swollen condition, they may be treated while in such condition with the saponifying agent.

The actual saponificationtreatment may be effected in any suitable manner. For instance the complete saponification may be effected in a bath treatment, in which case a long bath may be provided, or a comparatively short bath to which heat is applied, or the yarns may be simply padded or otherwise provided with a limited quantity of the saponifying agent which is caused to act subsequent to the application thereof, for example by passages over heated drums in the manner described in U. S. Patents Nos. 1,884,622 and 1,884,623. The application of the saponifying agent will usually be a uniform application over the whole length of the yarn, but the inven.-'

tion does not exclude the intermittent application of the saponifying agent as described in U. S. application S. No. 415,803 filed 21st Decem- I ber, 1929 for the purpose of obtaining fancy yarns or fabrics. A further alternative consists in spraying the sapomfying agent on to the yarns or fabrics .in a uniform manner or applying the saponifying agent, for instance ammonia or an organic base, in the form of vapour, and in this case also local effects may be produced e. g. by the application of resists or the use of stencils.

The degree of saponification effected in accordance with thepresent invention will vary with the object which itis desired to achieve. Relatively low saponification, such as a saponification resulting in a loss of weight of 2 to 5 or 10 or 15% on the weight of the cellulose acetate, maybe applied with the object of conferring upon the material an affinity for cotton dyes or with the object of increasing the safe ironing point, though for this latter purpose a loss in weight of 10 to 20 or 30% or more is desirable. The invention also envisages a process in which the ester groups are completely or substantially completely eliminated from the cellulose ester so as to produce a. product which is wholly or almost wholly reconstituted cellulose and therefore resembles the artificial silks and other products made from viscose. In this connection reference is made to U. S. application S. No. 655,773 filed 8th February, 1933 which is particularly concerned with the production of regenerated cellulose materials.

In order to shorten the time of contact of the materials with the saponifying agent, and particularly in order to makeuse of the full length of the bath in bath treatments carried out while the materials are in motion,it may be advantageous to subject the materials to a previous treatment in order to wet them out thoroughly. Methods of effecting this are described in U. S. application S. No. 655,773.

The process of the invention maybe applied to the treatment of cellulose acetates or other saponifiable esters of cellulose, for instance cellulose iormate, propionate or butyrate, of all kinds. Esters of low, medium or high viscosity characteristics may be present in the treated yarns, fabrics or other materials, for instance cellulose acetates having a viscosity of 5l0, 20-30 or 50-100 or 200 or more as measured by comparing the viscosity of a 6% solution in acetone against a standard of glycerine taken as 100. The yarns or other materials treated may consist wholly of the cellulose ester or may contain other materials not deleteriously affected, as for instance natural or artificial cellulosic materials.

Furthermore the materials may be subjected to'a stretching operation before, during or after the saponifying treatment with a view to obtaining products of increased tenacity. This stretching of the yarns or other products may be carrled out by any suitable process, as for example those specifically described in -U. S. Patent No. 1,709,470 and U. S. application S. No. 378,684 filed 16th July, 1929, or the stretching in stages of U. S. application S. No. 573,424 filed 6th November, 1931. As described in U. S. application S. No. 602,844 filed 2nd April, 1932 considerable economy and other advantages accrue by carrying out the stretching operation with the yarns, threads. or the like in warp formation. Such a warp may be carried continuously through the stretching and saponifying operations. The saponification of a number of threads in warp formation either as a separate operation or continuously with the stretching operation is described in detail in U. S. application S. No. 655,773 to which reference is made.

The saponification process of the present invention may also, be applied to artificial filaments, threads and similar materials which have been intermittently stretched, for example according to the processes described in U. S. applications 8.

Nos. 573,422 filed 6th November, 1931 and 574,852 filed 13th November, 1931, and to the fabrics and other products-containing such materials, as described in U. 8. application 8. No. 665,630 filed April 12, 1933.

Instead of treating the materials during their travel from one point to another they may, if desired, be treated in the form of hanks or cakes or other packages, and such processes are particularly useful when'applied to cakes of yarn obtained by collection in a centrifugal spinning box. In this connection reference is made broadly to U. S. application S. No. 655,773 in which details of suitable methods of carrying out such saponification are described.

The stretching may be facilitated by means of solvents or swelling agents for the cellulose acetate or other cellulose esters, or for cellulose in the case of stretching after a more or less complete saponification, for example aqueous solutions of thiocyanates, such as those-of the alkalies, ammonium and alkaline earths, aqueous solutions of zinc chloride, acetic acid, formic acid, lactic acid, diacetone alcohol, acetone and the like; the ethers cyclic and non-cyclic, esters or ether-esters of olefine glycols and polyolefine glycols or of other polyhydric alcohols, for instance the monoand di-methyl and ethyl ethers of ethylene glycol, the mono-methyl and ethyl ethers of propylene glycol, and the mono-ethyi ether of diethylene glycol, dioxane, methylene ethylene dioxide and their homo'logues and substitution products, glycol monoacetate, methyl glycol monoacetate, mono-, diand tri-acetins, etc.; phenols, formaldehyde, acetaldehyde, dichlorethylene, methylene chloride and the like, or mixtures of these, or solvent mixtures. Such processes of stretching may be applied either to wet or to dry spun yarns, and low degrees of stretch e. g. -100% of the original length of the materials may be applied, though preferably the stretch is considerably greater, e. g. 400500%. The yarn may be stretched after its formation either continuously or 'discontinuously with its production, and/or it may be stretched consid--' erably during its formation. In dry spinning operations this involves a softening treatment during the dry spinning process so as to enable a during, continuously with or after their forma-.

tion may be such as-to impart to the threads an initial tenacity exceeding 1.5 grams per denier and preferably exceeding 2 or even 2.5 or more grams per denier.

Such a stretching of the materials and also the use of high viscosity esters may still further increase the dry tenacity of the saponified materials obtainable in. accordance with the invention.

The following examples illustrate the invention but it is to be clearly understood that they do not limit it in any way'.

: EmmpleI A warp of celluloseacetate yarn, either bowl padding mangle in which it is impr gnated with a saponifying solution of the following composition:

7 parts of caustic soda 3 partsof Turkeyredoil 90 parts of water The nip of the mangle is adjusted so that the yarn retains about its own weight of liquor and the warp is carried directly-from the padding mangle to a series of hollow steam heatedrollers to'eifect saponiflcation as described in U. S. Patents Nos. 1,884,622 and 1,884,623. Subsequently it is scoured to remove the oil and other substances. Y

Example 2 An olive oil emulsion containing a saponifying agent is made up in the following manner, the parts being by weight:-

2 Parts of triethanolainine 10 Parts of oleic acid j. 30 parts of olive oil are thoroughly stirred until an approximately homogeneous mixture is obtained and then 33 parts of water are added with constant stirring stretched or unstretched, is carried over a 2 or 3 until a thick, smooth emulsion is obtained. 60

. in gradually increasing quantities.

A number of celiulose acetate dry spun yarns in warp formation. as spun or after having been stretched to 400 or 500% of their original length, are led from a. creel of bobbins through a reed and between nip roilers in a wetting out bath, and thence over another roller through a further reed and under a roller in a saponifying bath containing the emulsion described above at a temperature of 40-50 C. The length of the bath is about 90-100 feet, and at the further end of the bath the warp passes through a reed close to a feed roller and out of the bath to washing,

drying and winding devices.

The speed of the yarns is about 40 metres per minute.

Example 3 An emulsion is prepared by stirring up about 1 part of light mineral oil with 20 parts of a 4% soap solution containing about -1% of caustic soda. A cellulose acetate yarn in hank or other form is then treated in the above emulsion for about 15 to 20 hours at 20 to 25 C. the ratio of the bath volume to the material treated being 20 to 40:1. When the desireddegree of saponification is obtained, the yarn is washed to remove the oil and other substances, and then dried. A partially saponifled yarn is thus obtained having an improved tenacity and extension and an afiini'ty for cotton colors. What I claim and desire to secure by Letters .Patent is:

1. Process for the :saponification of artificial filaments, threads, yarns, ribbons, fabrics and other materials containing organic esters of cellulose, which comprises treating the materials with an alkaline saponifying medium throughout which is distributed an oil.

2. Process for the saponification 01' artificial filaments, threads, yarns, ribbons, fabrics and other materials containing cellulose acetate, which comprises treating the materials with an aqueous alkaline saponifying medium throughout which is distributed an oil.

3. Process for the saponificatiomoi' artificial filaments, threads, yarns, ribbons, fabrics and other materials containing organic esters of cellulose, which comprises treating the materials with an aqueous saponifying medium containing a mineral alkali and a colloidally dispersed oil.

4. Process for the saponification of artificial filaments, threads, yarns, ribbons, fabrics and other materials containing cellulose acetate,

which comprises treating the materials with an aqueous saponii'ying medium containing a min-' eral alkali and a colloidally dispersed oil.

5. Process for the saponification of artificial filaments, threads, yarns, ribbons, fabrics and other materials containing cellulose acetate,

I which comprises treating the materials at a temperature of at least C. with an aqeous saponitying medium containing caustic soda in a con centration of from 3 to 5% throughout which is distributed an oil.

6. Process for the manufacture of strong artificial materials having an aflinity for cotton dyes, which comprises saponifying filaments, threads,

' yarns, ribbons and like materialscontaining oryarns, ribbons and like materials containing cellulose acetate which have been stretched by at least of their original length, by treatment at a temperature of at least 60 C. with an aqueous saponifying medium containing caustic soda in a concentration of from 3 to 5% throughout which is distributed an 011.

8; Process for the manuf cture of strong arti-' ficial materials having an a nity for cotton dyes, which comprises sapon'ifying filaments, threads, yarns,.ribbons and like materials containing cellulose acetate which have been stretched by at least 100% 01 their original length, by treatment at a temperature or at least 60 C. with an aqueous saponifying medium containing caustic soda in a concentration of from 3 to 5% throughout which isdistributed an oil so as to effect a loss in weight of the-order of 10% on the weight oi. the cellulose acetate.

v HENRY DREYFUS. 

